Disk I/O Issues

• Disks are very often the bottleneck

• If the CPU isn't nearly saturated, check disk I/O stats: vmstat, iostat, sar, etc.

• Low seek times are your friends

• SCSI disks use tagged command queuing

  • Better for multi-threaded random I/O
  • IDE disks don't, but the kernel may try

• RAID-0 or manual I/O balancing help